Fix token form 30 days example (#24117)

Author: ousmaneo

graylog2-web-interface/src/components/users/CreateTokenForm.tsx

@@ -98,7 +98,7 @@ const CreateTokenForm = ({
         {creatingToken ? <Spinner text="Creating..." /> : 'Create Token'}
       </Button>
       <HelpBlock>
-        TTL Syntax Examples: for 60 seconds: PT60S, for 60 minutes PT60M, for 24 hours: PT24H, for 30 days: PT30D
+        TTL Syntax Examples: for 60 seconds: PT60S, for 60 minutes: PT60M, for 24 hours: PT24H, for 30 days: P30D
       </HelpBlock>
     </StyledForm>
   );